Effect of polyvinylpyrrolidone molecular weight and concentration on its dual role in the synthesis, stability and antimicrobial activity of silver nanoparticles

Silver nanoparticles are widely synthesized for various applications, including antimicrobial coatings, biomedical devices, and others. Traditional silver nanoparticle synthesis methods often rely on hazardous reducing agents, which pose risks to both human health and the environment. Using polymers like polyvinylpyrrolidone as both reducing and stabilizing agents eliminates the need for additional chemical reducing agents. The pH was adjusted with NaOH to facilitate reduction by PVP, aligning with environmentally benign chemistry principles. While PVP is widely used as a stabilizer, its potential as a reducing agent and the influence of its molecular weight and concentration on nanoparticle synthesis remain insufficiently explored. This study provides new insights into the role of molecular weight of polyvinylpyrrolidone on synthesis, size, stability and antibacterial properties of silver nanoparticles. The findings of this study suggest a complex interplay between molecular weight and concentration of the PVP on the synthesis and shape of the silver nanoparticles. The silver nanoparticles were synthesized at pH 11 for all the PVPs except PVP 1300 K. At pH 9, low molecular weight PVP, such as PVP 10 K and PVP 40 K were able to synthesize silver nanoparticles. Synthesis by PVP360 yielded a significant proportion of nonspherical or anisotropic nanoparticles (triangular and hexagonal) as confirmed by TEM. Nanoparticle suspensions demonstrated good stability up to 6 months. The antimicrobial efficacy of the particles was strongly dependent on the concentration of the PVP, while molecular weight did not impact the size of the inhibition zone in the well diffusion test. The higher concentration of PVP reduced the leaching or diffusion of the silver ions, leading to a reduced size of inhibition zones.